486 CHAPTER 9. FIELD EFFECT TRANSISTORS: MOSFET
n+-doped regions. The other parameters for the device are the following:
Vfb = − 1 .0V
μn = 500 cm^2 V−^1 s−^1
μp = 100 cm^2 V−^1 s−^1
Gate length = 2. 0 μm
Gate width = 20. 0 μm
dox = 500A ̊
(a) Calculate the channel conductivity near the Si-SiO 2 interface under flat band condition
and at inversion. Use the conditionVs=2φFfor inversion.
(b) Calculate the electron and hole densities at the Si-SiO 2 interface on the source and
drain side of the gate when the gate bias isVT+0. 5 VandVDS=1. 0 V.
(c) Calculate the saturation current in the channel for the gate bias specified above.
(d) If the gate voltage is such that the Si bands are flat,estimatethe current density in in
the channel for a drain bias of 1.0 V.
Problem 9.2Consider ann-MOSFET made from Si-dopedp-type at
Na=5× 1016 cm−^3 at 300 K. The other parameters for the device are the following:
Vfb = − 0 .5V
μn = 600 cm^2 V−^1 s−^1
μp = 100 cm^2 V−^1 s−^1
Gate length = 1. 5 μm
Gate width = 50. 0 μm
dox = 500A ̊
The inversion condition isVs=2φF.
(a) Calculate the threshold voltageVT.
(b) Calculate the channel current when the gate bias isVT+1. 5 Vand the drain bias is
1.0 V.
(c) Estimate theratiooftheelectronvelocities in the channel on the source side and the
drain side of the gate for the biasing in part (ii).
Problem 9.3Consider an n-MOSFET made from Si dopedp-type at
